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his investigation deals with the influence of hot and temperate curing environments on the hardened properties of concrete and mortar mixes. Condensed silica fume was blended with OPC as a potential alternative cementitious material to plain OPC for use in the hot Iraqi climate, in an attempt to find a cement combination that would overcome some of the durability problems experienced when using a plain OPC concrete in such an environment. Throughout the investigation two curing environments were used: the first simulating the UK temperate climate and the second simulating the hot Iraqi climate. Temperature and humidity were varied to simulate day and night time. The first stage of the experimental study was the development of a mix design method capable of producing an OPC-CSF cement concrete of a medium workability and a specific 28-days compressive strength ranging between 25 to 55 MPa, both with and without superplasticizer. Three grades of concrete strength were chosen (25,40 and 55 MPa) and the effect of four cement replacement levels (5,10,15 and 20%) of silica fume on concrete compressive strength was assessed. Test results showed that CSF was relatively more effective in lean mixes than in rich ones. Compressive strength of CSF concrete increased with increasing CSF percentages for both normal and superplasticized mixes up to an optimum levels of 10-15% and 15-20%, respectively. The amount of OPC (kg/m`3) necessary to bring a change in compressive strength of 1MPa was also determined and the theoritical blend proportions of OPC-CSF necessary to produce 28-day compressive strength equivalent to the plain OPC mixes were determined from the produced data above. The theoretical blend proportions were examined experimentally and the data were used to establish the relationship between strength and water/cementitious ratio for the blend mixes with and, without superplasticizer. Results showed that this basic relationship had changed quantitatively but not qualitatively when CSF was used. A cost study using current OPC and CSF material costs -was performed in an attempt to determine'the- most economic blend proportions. A total of eleven different concrete -mixes were selected to study the effect of curing environment (hot and temperate), initial curing time (0,1,3 and`-7 days) and curing method (water and polythene sheeting) on the compressive strength, permeability and absorption properties of the CSF concretes. Tests were carried out at 3,7, '14, 28,56,90 and 180 days of age. In addition five different mortar, mixes were used to examine the effect of curing environment (temperate and hot) an the *permeability, pore size distribution and durability to magnesium sulphate attack. Test results showed that hot Iraqi curing environment was favourable to the early-age strength, absorption and permeability of plain OPC mixes. However, - the later-age properties were significantly lower than those obtained for concretes cured in a temperate UK environment. For plain OPC mixes a critical curing period of 3 days was found under both temperate and hot environment. For the CSF blend mixes critical curing periods for the temperate and hot environment were found to be 3 and 1 day respectively. Results also reveal the importance of curing specimens immediately after casting for one day. Research work has also confirmed the superiority of water curing over polythene sheeting in a temperate environment for the rich plain OPC and CSF mixes. However, there was no significant difference between water and polythene for lean mixes. The reduction in , permeability and absorption properties of CSF mixes cured in a both temperate and hot environments is thought to be due to the changes in the pore structure brought about by the use of silica fume. Combining CSF with OPC was found to increase the percentages and volume of fine pores at the expense-of coarse pores. This effect may be described as a "refining" effect. Finally, the performance of CSF mortar mixes cured in a temperate and hot environment and their resistance to magnesium sulphate attack was significantly better than the plain OPC ones.

This thesis is concerned with the early-life behaviour of concrete industrial ground floors. Advances in construction methods are placing increased demands on the performance of industrial floors and pushing the limits of the current design guidance. Uncertainties about the true behaviour of industrial floors have been addressed by a programme of in-situ monitoring. An in-situ instrumentation methodology has been developed to monitor the slab and the local climate. Vibrating wire strain gauges and demecs were used to collect concrete shrinkage and joint performance data, whilst thermocouple arrays and thermistors in the strain gauges recorded the slab temperature. This allowed the effects of the cement hydration and the impact of ambient conditions on the slab to be assessed. The use of an automated data collection system allowed the timing as well as the magnitude of the movements to be measured helping identify cause and effect. Floor slabs covering long strip and large area pour construction, jointed and jointless detailing and mesh fabric and fibre reinforcement have been investigated. The data has shown the strong thermal influence on the behaviour of the slabs. Initial joint opening was found to be triggered by the cooling of the slab, whilst the effects of seasonal temperature changes in the first couple of months after construction could be as large if not larger than the drying shrinkage. Frictional resistance was found to reduce the measured movement, whilst the restraint arising from adjacent pours was also found to be significant. Finite element models of the temperature development have been produced using material property data found in the literature. Calibration and verification were carried out using the temperature data collected from site with good agreement. Structural models were then developed using the temperature and degree of hydration output from the thermal analysis as input. These models were used to determine the theoretical stress distribution in slabs at early-ages, and to conduct a parametric study. This demonstrated that the warping stresses present in a slab are generally greater than those from frictional restraint. The thesis concludes with recommendations for the design and construction of industrial ground floors.

This thesis is concerned with an experimental investigation of the behaviour of lapped joints in reinforced concrete. A review of existing literature highlights the need to establish the longitudinal strain distribution along lap joints. This has been achieved experimentally, with detailed strain measurements being taken using a technique of internally gauging the reinforcing rods. In some specimens, strain concentration gauges were installed at the tip of the lap to permit the acquisition of particularly localised information. Computer programs were developed to process the substantial amounts of data generated during the course of each test. Two series of tests were undertaken, both using axially loaded specimens, and dealing with tension and compression lap joints respectively. The laps ranged in length from 125 to 750 mm, and comprised bars of either 12 or 20 mm diameter. Transverse reinforcement was provided in two of the tension specimens. Greater emphasis was placed on the first series, with fifteen tension specimens being tested. Thirteen of these tests were each completed within a single day but, additionally, two long-term tests were undertaken. In the latter, a constant load was sustained for up to 81 days. The measurements clearly showed the changing behaviour of the specimens, first as transverse cracks developed and subsequently as failure of the lap joint was approached. The comprehensive analysis of the test results includes a comparison of the ultimate behaviour of these joints with existing design proposals and regulations. The detailed information provided by the strain measurements enables the justification of design assumptions regarding lap joint behaviour, and thus lends greater confidence to existing design regulations. The results from five compression specimens were analysed and compared with the tension tests. The significant contribution to force transfer made by the bearing of the free end of the steel against the concrete was evident. The specimens were loaded to the rig capacity without failing. Additional strain measurements were taken in one tension and one compression specimen by casting embedment gauges within the concrete. These gauges were arranged to measure the circumferential strains in the specimen, and were complemented by strain gauges mounted on the surface of the concrete. The data thus obtained permitted a comparison of the bursting forces set up inside and outside the lap joints. The work showed that some aspects of lap joint behaviour require clarification. Suggestions for further work are included.

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No description available.

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No description available.